The present invention pertains to a computer system comprising a host computer, a virtual storage subsystem, a storage subsystem, and a management computer. In particular, the present invention relates to a management unit for optimally maintaining the configuration of the computer system.
(1) Storage Area Network
A computer system where one or more external storage apparatuses and one or more host computers are connected via a Storage Area Network (SAN) and a plurality of host computers share high-capacity storage apparatuses configured from one or more external storage apparatuses is becoming widely prevalent. With this kind of computer system, there is an advantage in that it is easy to add delete or exchange the memory resource or computer resource, and that it is superior in extensibility. A storage subsystem configured in RAID (Redundant Array of Independent Disks) is generally used as the external storage apparatus to be connected to the SAN.
(2) Fibre Channel Zoning
Further, a fibre channel switch configuring the SAN provides a zoning function, which is a logical partitioning unit of a fibre channel network. One mode of fibre channel zoning configures one zone with an aggregate of network interfaces, The network interfaces registered in the zone do not accept the data transfer with a network interface that is not registered in the zone. In other words, data transfer is enabled only among the network interfaces registered in the zone.
(3) Hierarchical Storage System
Japanese Patent Laid Open Publication No. 2005-011277 (Patent Document 1) proposes a computer system capable of alleviating the load of one's own virtual storage subsystem by connecting a virtual storage subsystem to an external storage subsystem having another storage extent, and providing to a host computer the storage extent in such other storage subsystem as a virtual storage extent of one's own virtual storage subsystem.
Further, Japanese Patent Laid-Open Publication No. 2005-242690 (Patent Document 2) proposes a computer system wherein a storage extent provided by an external storage subsystem is defined as a virtual storage extent of one's own virtual storage subsystem so as to relay all I/O processing request from a host computer. During the relay, the I/O processing status is monitored and, when there is an external storage subsystem with a high load, the operational status of the port and processor is confirmed. When the load can be suppressed by changing the configuration thereof, such change Is performed, and, when it is not possible to suppress the load by changing the configuration, data is migrated from the virtual storage extent with a high load to a more available virtual storage extent, or from the storage extent with a high load to a more available storage extent.
Moreover, Japanese Patent Laid-Open Publication No. 2004-127141 (Patent Document 3) proposes a computer system of acquiring information managed by the respective apparatuses from an administrator of the respective apparatuses connected to a SAN, detecting virtual storage extent mapping and real storage extent mapping in the SAN based on the acquired information, managing these, retaining an event dictionary for interpreting the contents of a failure notice message received from the respective apparatuses in the SAN, and, upon receiving a failure reception message, detecting the influence of such failure on the I/O access of the virtual storage extent, and checking the virtual storage extent creation request of the SAN administrator based on the virtual storage extent mapping information or real storage extent mapping information.
The virtual storage subsystem technology disclosed in Patent Documents 1 to 3 seeks to equalize the load by migrating a virtual storage extent with a high load to a separate virtual storage subsystem. As this virtual storage subsystem to become the, migration destination, it is necessary to select a virtual storage subsystem to which the I/O devices to be connected to the virtual storage extent to be migrated can 1i similarly be connected. Nevertheless, if the configuration of the Storage Area Network is complex, it becomes difficult to select a virtual storage subsystem that satisfies the foregoing requirement. For instance, the virtual storage subsystem of the migration destination must be selected as follows.    (1) As the virtual storage subsystem of the migration destination, it is necessary to select a virtual storage subsystem that is physically connectable to all I/O devices that were connected to the virtual storage extent to be migrated.    (2) In a case when the virtual storage subsystem has a function of partitioning a network into logical areas, as the virtual storage subsystem of the migration destination, it is necessary to select a virtual storage subsystem that is logically connectable to all I/O devices that were connected to the virtual storage extent to be migrated.    (3) When there is no virtual storage subsystem that satisfies the requirements of (1) and (2) above, it is necessary to change the network configuration so that all I/O devices that were connected to the, virtual storage extent to be migrated can be connected to the virtual storage subsystem of the migration destination.
In other words, during the process of migrating a virtual storage extent loaded in a virtual storage subsystem to a separate virtual storage subsystem, all I/O devices to be connected to such virtual storage extent must also be able to reliably connect to the virtual storage subsystem of the migration destination. Thus, in selecting the virtual storage subsystem of the migration destination, a means for selecting a virtual storage subsystem capable of guaranteeing that all I/O devices to be connected to the virtual storage extent can be connected in the physical configuration and logical configuration of the network will be required. Further, if there is no virtual storage subsystem that satisfies the foregoing requirements, a means for changing the logical network configuration so that all I/O devices can be connected to the virtual storage subsystem after migration will be required.